Washington state workers remove an SUV and pickup truck from the deck of the collapsed Skagit River bridge in Mount Vernon, Wash. A temporary replacement bridge will open Wednesday.

British Columbians driving to Seattle and further south will be relieved that a temporary bridge over the Skagit River is set to open today after a month of delays and detours on B.C.'s most important trade route to the United States.

Washington Gov. Jay Inslee Tuesday announced that a temporary span on the Interstate-5 bridge across the Skagit River in Mount Vernon, Wash. will be ready for use today.

After the span collapsed on May 23, Inslee set a goal of restoring it by mid-June. He went to Mount Vernon on Tuesday to inspect the span and announce the reopening. He praised workers for completing in days what normally would have taken months.

Staying on I-5 could shave as much as half an hour off a car trip from Blaine, on the American side of the border, to Seattle for drivers who have faced major delays while lining up to detour through Mount Vernon and Burlington.

However, the bridge will remain a bit of a bottleneck because the 49-metre-long temporary span is narrower, at 7.3 metres wide, than the one it replaces.

The state Transportation Department said Tuesday traffic will have to slow to 40 miles an hour (64 km/h) on the narrow temporary span, and oversized or overweight loads will continue to be detoured until a permanent fix in the fall.

Still, the temporary span will carry 99 per cent of I-5 traffic, said state Transportation Secretary Lynn Peterson.

The I-5 is a critically important trade link with 71,000 vehicles using it daily in north Washington. It is one of America's busiest highways, stretching from the U.S.-Mexico border in San Diego to the Canadian border, a ribbon threading through almost all the major cities on the West Coast. It links directly with B.C.'s Highway 99, and is a vital conduit for the goods and traffic that fuel the two countries' economic engines.

The temporary span and a permanent replacement due this fall will cost nearly $18 million. The U.S. federal government is paying for all but about $1 million of the work.

The temporary bridge pieces were supplied by Acrow Bridge through an emergency contract the Transportation Department signed with Atkinson Construction.

The Max Kuney construction company of Spokane was selected Tuesday for the permanent replacement, Peterson said.

Because the 58-year-old bridge is being restored, not replaced, it will still be rated as "functionally obsolete" because it was not designed to handle today's traffic volume and big trucks.

It's also "fracture critical," meaning that if a single, vital component is compromised, the bridge can crumple again.

The Alberta driver of the oversized truck the damaged the bridge felt crowded by another southbound semi-truck on the bridge and shifted right. His load struck a side girder, setting off a structural failure that caused one section of the bridge to fall, a preliminary U.S. National Transportation Safety Board report said.

While the truck made it safely onto a span that did not drop, a car and pickup truck went into the water and three people were rescued.